RE ca, ites Eo akc} 
» Oey oe 
aa 
LL. Lesquereux— Rocky Mountain Lignitic Formation. 448 
of our Cretaceous species, only smaller; and Unger, in Flora of 
tska. has named Platanus Sirit, a leaf still more similar to 
ours. These leaves are considered by other authors as refera- 
ble to the genus Acer. This does not make any difference. 
They represent a type of our Cretaceous and of the Miocene 
of Kurope; as yet not seen in our Eocene. It is the same with 
Acer (maple) and Quercus (oak.) They are marked in our Cre- 
eous, the first by Acer obtusilobum, with characters of leaves 
seen again in the Kuropean Miocene, and at our present time 
on both continents; the second by a species related to some 
varieties of our chestnut-oak, and by two others comparable by 
the form of their entire leaves to our shingle-oak (Quercus im- 
bricaria Michx.) Both these types are most common in the 
Miocene of Europe; but, like that of the Cretaceous maple, 
they have not as yet been observed in our Lignitic Eocene. 
The leaves which I have considered as of a Juglans, and which 
Heer refers to Populous, P. Debeyana, are of uncertain affinity. 
Their analogy has not yet been recognized out of the Cretaceous. 
could pursue to some length the examination of analogies 
of this kind, which may be considered as negative characters 
of the American Eocene. Besides establishing the remarkable 
relation of the American Cretaceous flora with the Miocene 
cibly still elicit the same conclusion. From the beginning, In 
the examination of the sandstone of the Raton, I have recorded 
the great amount of fucoidal remains in this sandstone, as an 
essential character of its Eocene age. The irregularity of dis- 
tribution of marine vegetable remains in the geological groups 
has been remarked by every paleontologist. The oldest forma- 
tion, the Silurian and the Devonian, have an abundance of them. 
The Carboniferous, except at its base, as also the Trias and the 
Permian, have scarcely any. In the Jurassic they begin to re- 
1 rd to their maximum 
ferable. I found it upon pieces of limestone cove 
Species of large niotheskd characteristic of this group. es 
y Bronguiart to the Dictyotites, by Geinitz to the — y 
Schimper to the e/eanpaulia of the Marsileacew, by Schenck to 
